On the Arrangement of the Vascular Strands in the 
‘Seedlings’ of Certain Leptosporangiate Ferns 1 . 
BY 
S. E. CHANDLER, D.Sc., A.R.C.S., F.L.S. 
Assistant in the Colonial Collections at the Imperial Institute. 
With Plates XVIII, XIX, and XX. 
B EFORE the publication of Jeffrey’s 2 account of the development of 
the vascular system of Pteris aquilina y very little attention had been 
paid to the ontogeny of the ‘ polystelic ’ type of vascular anatomy. 
Gerard 3 , Van Tieghem 4 , and Leclerc du Sablon 5 had described the 
very earliest transitional stages of several ferns, but in the majority of 
cases the descriptions were of the shortest character, and merely concerned 
with the anatomical changes involved in the transition of the diarch root- 
structure to the solid protostele occurring at the base of the young stem. 
These researches, although in themselves of considerable interest, threw 
very little light upon the processes involved in the vascular elaboration, 
and it was not until Jeffrey published his account of Pteris that definite 
and accurate information upon this important point was available. 
Since the appearance of Jeffrey’s paper, much work has been done 
along exactly similar lines for other ferns, both by that author himself, 
and also by Boodle, Gwynne- Vaughan, Farmer and Hill, and others. As 
a result, botanists at the present time have a good general idea of the 
development of a typical dictyostelic vascular organization, though the 
interpretation of the facts observed varies to no small degree. 
In spite, however, of the considerable amount of work which has been 
done in this direction, definite information with regard to particular species 
1 Accepted by the Senate of the University of London as a Thesis for the Degree of Doctor 
of Science. 
2 Morphology of the Central Cylinder of Angiosperms. Trans. Canad. Inst., 6. 1900. 
3 Recherches sur le passage de la racine a la tige. Ann. Sc. Nat., 6° s6\, t. xi. 
4 Snr la Polystelie. Ann. Sc. Nat., 7 e s6r., t. iii. 
5 Recherches sur la formation de la tige des Fougeres. Ann. Sc. Nat., 7 e ser., t. xi. 
[Annals of Botany, Vol. XIX. No. LXXV. July, 1905.] 
